Azoxystrobin was a strobilurin fungicide discovered and commercialized by Zeneca company first, its chemical name is methyl (E)-2-{2-[6-(2-cyanophenoxy) pyrimidinyl-4-oxy]phenyl}-3-methoxyacrylate, and its structural formula is shown in formula (4):

This compound is an efficient and broad spectrum fungicide, can prevent and control almost all diseases resulted from fungi, oomycetes, phycomycetes, ascomycetes, and deuteromycetes, and is widely applied in foliage treatment and seed treatment of crop plants.
Two compounds with structural formulae shown in formula (1) and formula (2) respectively are key intermediates for preparing azoxystrobin in the industry. A typical preparation method for the two compounds is disclosed in patent document WO92/08703. The preparation method is as follows:

Where, the chemical name of the compound represented by formula (3) is 3-(α-methoxy) methylene benzofuran-2-(3H)-ketone. The compound represented by formula (3) reacts with sodium methoxide, and then reacts with 4,6-dichloropyrimidine, to obtain a mixture of the intermediates represented by formulae (1) and (2). The reaction takes 20-43 h. The reaction is poor in selectivity, it is difficult to separate the products, the yield ratio of azoxystrobin obtained finally in the follow-up reaction is approx. 40%, and the azoxystrobin product is poor in quality and is in dark brown color.
In patent document CN102311392A, an improved method is reported. In that method, a catalyst 1,4-diazabicyclo[2.2.2]octane (DABCO) is introduced after the compound represented by formula (3) reacts with sodium methoxide and thereby the compound represented by formula (8) is obtained. Under the catalytic action of the catalyst, the compound represented by formula (8) reacts with 4,6-dichloropyrimidine to obtain an intermediate represented by formula (1); the compound represented by formula (1) is transformed into the intermediate represented by formula (2) under the action of KHSO4. The reported chemical reaction process is as follows:

Since a catalyst DABCO is introduced, that method improves the reaction rate of the reaction between the compound represented by formula (8) and 4,6-dichloropyrimidine; hence, the reaction time is greatly shortened, and the process can be completed within 1.5 h.
However, the above-mentioned techniques have the following drawbacks:
1) In the processes described in WO92/08703 and CN102311392A, the compound represented by formula (3) reacts with sodium methoxide to generate the compound represented by formula (8) first. Owing to the fact that the reaction is a strong exothermic reaction, the compound represented by formula (8) produced in the reaction is unstable, and may be transformed into the compounds represented by formulae (9), (10), (11), and (12) when it is subjected to heat or stored in a long time, resulting in compromised yield ratio. Especially, when the technical scheme is applied at an industrial scale, the reaction time will be prolonged severely because a great deal of heat is produced in the reaction; consequently, such subsidiary reactions will happen more strongly, and the yield ratio of the reaction will be compromised.

2) The reaction between the compound represented by formula (8) and 4,6-dichloropyrimidine is also an exothermic reaction, and the reaction process is very sensitive to the reaction temperature. When the temperature is low, the reaction rate will be decreased severely; when the temperature is too high, a conjugate product as shown in formula (15) will be formed. Since 4,6-dichloropyrimidine is solid, usually it can be added in one operation or in batch only; in the existence of a catalyst DABCO, the reaction rate will be increased greatly; consequently, such an adding approach results in uneven heat release in the reaction, it is difficult to control the reaction temperature, and more conjugate products may be produced, resulting in compromised yield ratio of reaction.

3) In the process of transformation from the intermediate represented by formula (1) into the intermediate represented by formula (2) as described in WO92/08703 and CN102311392A, both the intermediate represented by formula (1) and the intermediate represented by formula (2) are viscous liquids, while the catalyst potassium bisulfate is solid; hence, it is difficult to solve the solid-liquid mixing problem (i.e., stirring problem) in mass industrial production.
In view of the problems described above, the present invention discloses an innovative method, with which the reaction process can be controlled easily, and the operation is simple and convenient, and the method is more suitable for use in mass industrial production.